This invention relates to chlorine, and more particularly, it relates to a method of producing chlorine from chlorocarbon compounds such as hexachloroethane.
Chlorine is widely used in treatment of molten metals such as aluminum to remove dissolved alkali elements, e.g., sodium, potassium, and the like. In addition, chlorine in conjunction with a carrier gas can facilitate removal of hydrogen and inclusions. Aluminum producing facilities can use in excess of 2000 pounds of chlorine per day for fluxing.
While the use of chlorine for treating molten aluminum is highly desirable, its use is not without problems. For example, railroad tank cars, typically containing 60 tons of chlorine often require entire towns to be evacuated when a local derailment occurs. Another concern is maintaining the tank cars or chlorine-containing cylinders in the plant to prevent leaks. That is, chlorine is a highly active chemical and is corrosive to the gas distribution hardware leading to chlorine leaks. Chlorine leaks are very undesirable because of the highly toxic nature of chlorine, which has an OSHA ceiling limit concentration of 1 ppm.
The health hazard presented by chlorine is illustrated by a foundry operation, for example, which typically would use cylinders containing 150 pounds of liquid chlorine. The 150 pounds of liquid chlorine will vaporize to produce 790 standard cubic feet of chlorine gas. Uniformly mixed with air, this quantity chlorine is sufficient to contaminate 790,000,000 cubic feet of airspace. In larger operations where 1 ton to 30 ton cylinders are used, it will be seen that the problem of leakage can be greatly exacerbated. Because of the potential environmental and industrial problems, the use of chlorine for fluxing or treatment of molten metal is often avoided even though it is technically superior to halocarbons and sulfur based compounds such as sulfur hexafluoride.
Thus, it will be seen that there is a great need for a process that permits the use of chlorine for fluxing, for example, without the transportation and containment problems. The present invention provides a solution to such problems and permits the use of chlorine without the attendant problems and storage.